This invention relates to fusible elements, and more particularly to a fusible link.
Fusible elements have long been known. These elements are temperature responsive. At a predetermined temperature, the elements separate to enable the actuation of an alarm or other device or to render equipment inoperable or operable.
Generally, fusible elements work on the principle that multiple pieces are held together by a eutectic solder which liquefies at the eutectic temperature of the solder to enable the elements to separate when the eutectic temperature is reached. Generally, the use of fusible elements is fraught with difficulty because of the general weakness or the weakness of the solder weld and the general physical properties of the solder itself.
Some fusible elements are unsatisfactory because they tend to xe2x80x9ccreepxe2x80x9d, i.e., tend to allow slippage to occur between the fusible parts at temperatures lower than the eutectic temperature or loads higher than solder itself will hold, rather than a clean separation when the eutectic temperature is reached. This slippage may cause a malfunctioning of the fuse. Creep is especially experienced when the fusible element is under tension under use. It is therefore highly desirable to provide a new and improved fusible element. It is also highly desirable to provide a new and improved fusible link which may bear a load with a smaller surface area than now required beneath the eutectic temperature without creep.
Other fusible elements fail because it has been found that the solder is unable to completely fill the space between the confronting or superimposed surfaces of the fuse, thereby developing voids and a weakness of the fuse. Therefore, it is also highly desirable to provide a new and more reliable fusible link without solder voids between the superimposed faces of the fuse.
Because of the weakness of eutectic solders, fusible elements usually are designed to subject the solder only to shear stresses. Whenever stresses, which are transverse to a shear stress are applied, the solder may tear or otherwise fail, again resulting in a malfunctioning of the fuse. Therefore, it is also highly desirable to provide a new and improved fusible link in which the stresses applied to the eutectic solder of the fusible element are all in shear.
Additionally, it is highly desirable that when the predetermined eutectic temperature or a eutectic temperature within an acceptable temperature range is reached, the fusible element separates cleanly. It is therefore highly desirable to provide a new and improved fusible link which breaks cleanly at the eutectic temperature and can bear a greater ambient temperature without failure.
Prior use of eutectic solders has always been accompanied with fire hazards and chemical waste hazards. Applying eutectic solders usually requires the solder to be applied in a melted form requiring the open flame of a torch. Additionally, solder fluxes are used which vaporize into hazardous gases and solidify into droppings which include hazardous chemical waste.
It is also highly desirable to provide a new and improved fusible link which utilizes the physical properties of the eutectic solder most desirably.
Finally, it is highly desirable to provide a new and improved fusible link which has all of the above desired features.
It is therefore an object of the invention to provide a new and improved fusible element.
It is therefore an object of the invention to provide a new and improved fusible link which may bear a load with a smaller surface area than now required beneath the eutectic temperature without creep.
It is therefore an object of the invention to provide a new and more reliable fusible link without solder voids between the superimposed faces of the fuse.
It is therefore an object of the invention to provide a new and improved fusible link in which the stresses applied to the eutectic solder of the fusible element are all in shear.
It is therefore an object of the invention to provide a new and improved fusible link which breaks cleanly at the eutectic temperature and can bear a greater ambient temperature without failure.
It is therefore an object of the invention to provide a new and improved fusible link which utilizes the physical properties of the eutectic solder most desirably.
Finally, it is therefore an object of the invention to provide a new and improved fusible link which has all of the above desired features.
In the broader aspects of the invention there is provided a new and improved fusible link having opposite ends. The fusible link comprises two pieces each having opposite ends. One of the opposite ends of each piece defines the opposite ends of the link. The other end of said pieces overlap each other and have a eutectic solder therebetween. Means is provided adjacent the other end of the pieces to strengthen the link in tension between the opposite ends when said solder is in shear and to reduce creep. Means is also provided adjacent the other ends of the pieces to separate the pieces and break the linkage upon the eutectic solder reaching the eutectic temperature. The new and improved fusible link in a specific embodiment utilizes a crimp and crimp sliding surfaces to prevent creep at temperatures lower than the eutectic temperature for providing separation of the link upon the solder being heated to a eutectic temperature.